Understanding Power Factor and How it Affects Your ...

1 Understanding Power Factor and How it Affects your electric BillPresented byScott Peele PEUnderstanding Power Factor Definitions kVA, kVAR, kW, Apparent Power vs. True Power Calculations Measurements Power Factor Correction Capacitors System Impacts I2R losses, Chapter 9 NEC Equipment sizing Power Factor Charges Problems with adding Caps Harmonic resonance Volt rise Power Factor vs Load FactorWhat is Power FactorPower Factor is the cosine of the phase angle between current and Factor is the ratio of true Power to apparent Alternating CurrentAC60 Hertz/secondDurationTimeMagnitudeVoltage Level169 volts120 Volts RMSOne Cycle .01666 secondsPhase Angle-200-150-100-500501001502000 DurationDegreesMagnitudeVoltage Level90120 Volts RMSOne Cycle 180270360ooooThree Basic Circuits or Loads Resistive Inductive Capacitive Or any combination Resistive Inductive Inductive Capacitive Resistive Capacitive Resistive Inductive CapacitiveTypes of Loads Resistive Incandescent Lamp Resistance heat Inductive Motors Contactor Coils Relays (coils) Capacitive Capacitors Start Capacitors Run Capacitors Power Factor Correction CapacitorsResistive LoadsIn Phase-200-150-100-500501001502000 MagnitudeLevelDurationTimeInductive LoadsLaggingDurationTimeMagnitudeLevel-2 00-150-100-500501001502000 Capacitive LoadsLeadingDurationTimeMagnitudeLevel-2 00-150-100-500501001502000 What is Power Power is measured in Watts.

2 Volts X Amps X Power Factor = Watts Watts only equals Volts X Amps when the Power Factor is 1 or unity. Most of the time the Power Factor is less than 1. Power = Watts : True Power Volts X Amps = VA : Apparent PowerUnderstanding Right Triangles Right Angle 900A= Side OppositeB= Side AdjacentPower Triangle A= Side OppositeB= Side AdjacentTrue powerApparent powerPower Factor = Power Factor =Cos= Adjacent sideHypotenuseCos Right Angle 900A= Side OppositeB= Side AdjacentTrue powerApparent powerPower Factor =True Power Reactive PowerUnderstanding Power Triangle A= Reactive PowerVAR, kVAR ReactanceB= True PowerWatts, KW, PowerGraphical representation of resistance, reactance, and impedanceInductiveMotorsR InductiveReactanceResistanceXGraphical representation of resistance, reactance, and impedanceCapacitorsR CapacitiveReactanceResistanceXCapacitive CapacitorsInductiveMotorsReal -WATTS kW (KWH over Time) kVARR eactanceImaginaryImaginaryCosine of Power FACTORTrue Power = KW Load (resistive)= KVAR Load (reactive)

3 10 HP 460 Volt 4 Pole MotorLoadPower FactorVAAmpsWattsVARAmps ReactiveAmps Resistive125% HP Energy Flow A= Reactive PowerVAR = 6593B= True PowerWatts =8592 Power Factor = .79 Measured Amps = Amps = Amps = KW Load (resistive)= KVAR Load (reactive)MotorTransformerConductor10 HP Adding Capacitance= KW Load (resistive)= KVAR Load (reactive)Measured Amps = Amps = Amps = A= Reactive PowerVAR = 6593B= True PowerWatts =8592 Watts =8592VA =8595 VAR = 1 MotorTransformerConductor10 HP Energy Savings= KW Load (resistive)= KVAR Load (reactive)Savingare calculated on I2R a # 12 gauge wire from Table 9 in the NEC the resistance is 2 ohms per 1000 feet. 200 @ 2 Ohms/1000 is .5 ohms. Using this the total saving will be approx. watts. NOTE: This is only if the capacitor is at the Feet of #12 Gauge 2X .5 = X = R = WattsMotorTransformerConductor10 HP Capacitor SizingUtility Meter= KW Load (resistive)= KVAR Load (reactive)I2R SavingsCapacitor to large then var flow in both directions and one may increase LossesExample of Power Factor ChargePF Charge FactorNC Charge$ Charge$ Billing Charge$ Charge$ kW Charge$ kWh Charge$ Total Charge$ Less than.

4 85 then a $ chargeFor kVar (kW ) In this Case $ on one month operation at 8 hours a day10 Horse Power MotorVA Watts VAR FactorVAWattsVAR125%115%100%75%50%25%Min Power Factor vs AmpsVoltsAmps VA kWPower Factor VAR Amps Reactive Amps Resistive Factor vs Amps020406080100120140160180123456789kWA mps Power Factor MotorTransformerConductor10 HP Voltage Rise= KW Load (resistive)= KVAR Load (reactive)kVAR * Xsource /kVA/100 = Voltage Rise %Note This does not include the wire inductance that will cause some additional rise in voltage. Note: With this voltage rise an increase in kW and kwh can Feet of #12 Gauge wireMVARMWP ower PlantGeneratorTransmission CircuitDistribution CircuitT/DSubstationSubstationCapacitor BankResidentialLoadIndustrialLoadCommerc ialLoad= KW Load (resistive)= KVAR Load (reactive)LLLS ystem VAR Requirements(Met by Power Plant Generator)KVARKWMWP ower PlantGeneratorTransmission CircuitDistribution CircuitT/DSubstationSubstationCapacitor BankResidentialLoadIndustrialLoadCommerc ialLoad= KW Load (resistive)= KVAR Load (reactive)LLLS ystem VAR Requirements(Met by Power T/D Substation)KVARKWMWP ower PlantGeneratorTransmission CircuitDistribution CircuitT/DSubstationSubstationCapacitor BankResidentialLoadIndustrialLoadCommerc ialLoad= KW Load (resistive)= KVAR Load (reactive)LLLS ystem VAR Requirements(Met by T/D Sub and Feeder Capacitors)

5 FeederCapacitorBankKVARKWT hings We have Talked About And Other Things to Talk About Phase Angle Power Factor I2R Loss Power Factor Penalty Voltage Rise Harmonic resonance Load Factor --- Power FactorHarmonic Resonance3 PHASE ACINPUT X SourceHarmonic SourceEquivalent CircuitX SourceX TX TX CHarmonic FiltersLL32L1 XFXCL1L2L3 Power Factor Vs Load Factor They have no relation Load Factor is kW at 100% operationYielding so many kWh vs. Actual kWhExampleHours in a Month = 30 X 24 = 720 HoursLoad is at 8 kW8 X 720 = 5760 kWh Actual kWh by load is 3240 Load Factor then is 3240/5760 Load Factor = .56 BOTTOM LINE ONUnderstanding Power Factor and How it Affects your electric BillzzVery small charge with penalty most customer have no Power Factor PenaltyNone or very small savings or possible increase cost when using Power Factor Correction DevicesQuestions